KANSAS CITY, Mo. (AP) Eric Thames earned a reputation as a workout warrior during his days playing professionally in South Korea, where he cultivated the prodigious power that served him so well last season with the Brewers.

Well, his leg muscles are going to be pretty strong in a couple months.

Thames joked Wednesday that he won't be able to exercise much else after an MRI exam revealed that he had torn the ulnar collateral ligament in his left thumb. The first baseman will head back to Milwaukee after his team wraps up its two-game set in Kansas City and be examined by team doctors, then likely schedule surgery in the hopes of returning for the second half of the season.

"Personally I feel like I let everybody down, but it's nothing I can control," said Thames, who was hitting .250 and second in the National League with seven homers. "I saw on (television) that I'll be out six to eight weeks, so I guess that's what it is. It all depends on when the surgery is."

The Royals recalled right-hander Brandon Woodruff from Triple-A Colorado Springs to take his place.

Thames hurt the thumb fielding a grounder in the eighth inning, but really felt the pain when he caught a dropped third strike from his catcher and the pain was intense. He headed to the dugout and told Brewers manager Craig Counsell, "I'm done."

Jesus Aguilar, who is hitting .429 with a homer and five RBIs, replaced him for the ninth inning, and he got the start on Wednesday night. Ryan Braun could also see some time at first base.

"It's certainly bad news. Eric's an important part of what we're doing. He's a big, left-handed bat that's not really replaceable," Counsell said. "But there are candidates to fill in there and I feel like really good candidates."

Indeed, the question in spring training was what the Brewers were going to do with their abundance of first basemen. That depth has now paid off for a team that had won seven straight entering Wednesday.

"You don't plan for this stuff but you try to anticipate what could happen," Counsell said. "I think we've been able to cover for a lot of what's happened so far and depth plays a part in that."

The Brewers have certainly weathered their share of injuries this season.

Outfielder Christian Yelich missed time earlier this month with an oblique strain, and right-hander Corey Knebel hurt his hamstring. Catcher Manny Pina just returned to the lineup Tuesday following a right calf strain, and catcher Stephen Vogt and reliever Boone Logan are also out.

Vogt left the clubhouse Wednesday for Arizona, where he will complete a throwing program in extended spring training. He hopes to test his ailing shoulder in minor league games later next week.

Logan was headed for Double-A Biloxi, where he will begin making rehab appearances following a triceps injury. Right-hander Wade Miley is already in Biloxi working back from a groin injury.